Episode 118 - River Systems

Fuelled once again by Christine's insatiable curiosity, today Talk Description to Me explores the visuals of river systems. How do rivers form? Are the headwaters obvious? Are stream networks visible in satellite images? Does a river in the Amazon look the same as a river in Egypt? With the help of diagrams, descriptions of maps, and tactile primers on continental geography, JJ and Christine dive headfirst into the cool, rushing waters of the world's great rivers.

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JJ Hunt: 0:03

Talk description to me is Christine Malec and JJ Hunt

Christine Malec: 0:27

Hi, I'm Christine Malec.

JJ Hunt: 0:28

And I'm JJ Hunt. This is talk description to me, where the visuals of current events and the world around us get hashed out in description rich conversations.

Christine Malec: 0:47

As with so many of our previous episodes, this episode came out of a kind of a lifelong curiosity of mine about river systems. And as someone who grew up blind, I, I kind of remember the moment it was, you know, shockingly late in my in my education process where, okay, I was still a kid, but where I realized rivers don't just start and flow straight down to the ocean and empty into it. They're really twisty and windy and complicated. And I didn't know that not having seen maps. And so the more I learned about them, the more I learned how complex they are. So today, we're going to talk about waterways, specifically river systems, and how they interact with the land and how the land interacts with them. And what what the behavior of river systems is, and we're going to definitely be looking at some specific examples, and how they fit into the landscape and what they do. So, JJ, for this, you use some satellite data and satellite images as a starting point, right?

JJ Hunt: 1:54

Yeah, I looked at some satellite images also looked at a lot of diagrams, I found that between the satellite images and the diagrams, you get a pretty decent understanding of the systems and how they work river or stream systems. When you look at them in a diagram, or sometimes in satellite images, they look like Bear trees, they've got these thick trunks with a wide base of major routes that are connected to a large body of water, like an ocean or a sea or lake or something like that, then then the big trunk that goes up from there, and then wide branches that come off of the trunk, these are the main tributaries, and then from there, smaller branches and twigs that come off of the main branches, these are the little streams, not kind of description is in reverse of the way it actually works. Of course, the water starts in those tiny little streams, those little twigs and branches, comes down toward the connect with enjoying the kind of, you know, larger branches of water, the tributaries, those then feed into the trunk of the tree that then come out into into the roots, which are like the deltas that connect to major bodies of water. And the diagrams of river systems, I think are often used in textbooks and in video explainers, diagrams that that really emphasize this pattern that I've just described. Because even when the satellite images are readily available, the diagrams can can really draw attention to those smaller streams and tributaries. In satellite images, those often get left out, because they just, they're just not, they're just not clearly visible. So a satellite image of a river system might be taken from hundreds, maybe even 1000s of kilometers above sea level, and a stream that's only 10 feet wide with, with trees growing on both sides of the bank, that's just not going to show up. I'm sure the experts can see the visual evidence I can cat you know, configure it, a little bit of it. But for the purposes of education, the diagram is often the thing.

Christine Malec: 3:58

So you already challenged an idea that I had by saying that the what you're saying is that the head of a river, like where it starts is not necessarily obvious. I always assumed like, oh, okay, that's the starting point. That's really obvious. But the way you're describing it is a little branch let's feeding into something bigger and bigger and bigger. And it's a bit almost like the reverse of how I pictured it. So is it ever unclear what the actual head of a river is like the actual starting point?

JJ Hunt: 4:30

Yeah, I think it is. Rivers are fed by lots of different types of water, right? You've got rainwater, you've got glacial melt. There's also groundwater ins and springs, those feed river systems as well. And so there are some areas where the clear part of the river the tributary or the stream that might be that might be clear, you know, there's a cut in the soil. There's a there's a you know, some kind of hollow in the land and and water is running down it, that's a stream that's clear. But the groundwater that kind of bubbles up and becomes swamp land, that's part of the river system as well. So the wetlands that feed into those streams, those are all part of the river system of a stream network. So the rainwater, the glacial melt, the groundwater, all of that flows into the small streams, those streams converge into branches, those gather into the main trunk, you know, so on and so forth. And then when they get close to the big body of water that they are releasing into, that's when you get these flat deltas, because a lot of the sediment has been carried down by the water deposited in this flat land that builds up this flat land. And then that's what floods and creates these deltas that then release into into the sea or the ocean and whatnot.

Christine Malec: 6:00

And so I guess you've answered my question that was brewing for me is, is that why a diagram might be more effective than a satellite image because it labels things and traces that out for you?

JJ Hunt: 6:14

That's right, it labels things, it traces it clearly. If you're looking at a satellite image, if you are an expert, you might know that this brown patch in the satellite image represents a kind of swampy area. And in that swampy area, we know that the elevation of that swamp is higher than this thin blue squiggle that appears, you know, a down, you know downslope from that, and so therefore, that water is feeding that stream. But to the layperson, who's looking at that, that might not be clear. Whereas if you have a nice arrow, blue arrow on a green piece of land that points like, here's where the, you know, here's the wetland, and here's where the stream is going. It's just more clear than a satellite. I've got an image of a satellite here, an example that I pulled up from the NASA's Earth Observatory website, this image was taken in 2019. This is, was taken at a time when the water levels in the Mississippi and the Missouri rivers in the southern US they were very, very high. This image is a high res full color satellite picture of the southern part of the Mississippi. And, you know, it's got state borders, overlaid and fine white lines, but it's mostly just about the geography here. Visually. This image shows the main trunk of the Mississippi running south from about the southeast tip of Missouri, near Kentucky and Illinois. But in fact, the river system actually starts far, far, far north of that it starts near the Canadian border. There's water that's pulled in from that far away. But it's not always clear in these satellite images in this satellite image of the lower half the lower portion of the Mississippi, the river system looks like a tall, narrow, windblown tree, that kind of leans a little bit to the right near the base of the tree kind of moving up, there's a branch that breaks off to our left into Louisiana, but the main trunk kind of angles up to our right, and that the trunk of the Mississippi that creates the divide between Louisiana and above it Arkansas, which is on our left or the West, and Mississippi and above it Tennessee to our right or to the east. And then about halfway up of Mississippi there's this wide blue patch that looks kind of like a knot or a burl if we're sticking with this tree metaphor. This is Delta National Forest part of the Mississippi's floodplain. And then above that north of the Louisiana Arkansas border, there's a branch that goes off to the left this creates a bit of a V shape that I believe is the Arkansas River going off to the left and the Mississippi that's the right side of the V shape and that carries on up and up and up up the top of our image and then again eventually fades away into this you know green area that is still feeding that's still the headwaters coming down from the south. So it's amazing and again keep in mind this roots up description that I've just given us backwards, the water flows from the tiny twigs, the which of the streams into the larger branches then into the trunk and I say that over and over again because visually, I sometimes find that hard to remember like when you write or water on the ground. It comes the water, you know flows from the source this bucket or whatever that you've dumped water out of. And then it slowly creeps out and becomes these You know, into little tiny streams or trickles along the earth. But in fact, this is the opposite the little tiny streams or trickles, that's where the water is coming from feeding into the big branch and then going into the major body of water, the lake or the sea or the ocean.

Christine Malec: 10:19

I play like to understand deltas better. And I feel like from my memory of a tactile map of the Nile, I feel like the Nile is a good example to start with, because unlike many rivers, it's it's actually sort of straight compared to other rivers. So can we kind of use that as an example and also and describe the delta that happens when it reaches the Mediterranean.

JJ Hunt: 10:42

So the Nile Delta is kind of extraordinary, because of just how green it is, compared to the rest of the landscape. You know, the Nile Delta is in Egypt, at the north end of the of the country where it reaches the Mediterranean. And yes, so the river, the Nile River has gone in a more or less straight line. And when you look at a satellite image, the Nile river looks green, because it is bordered by trees, vegetation growing right along either side of the relatively straight and narrow, for the most part, not that narrow, but it looks narrow compared to the deserts on either sides. On the satellite image, you've got desert to the right desert to the left, and then a relatively straight green thin line that comes up through the middle, that's the Nile and the vegetation on either side. And then as it approaches the Mediterranean in a satellite image, it fans out into a great big V. And everything in that is green, it's lush, there are things growing, this is the floodplain. And right along the border, like right along the shore, really of the Mediterranean, that's when you get city. So that's an urban center there right along. And so some within that green, there's kind of this green and gray patch, which is where it is urban, but there's still vegetation, there's still life. And that's what it looks like when it is when things are lush, if you look at the diagram of that, you can actually see individual like rivulets, you can see little streams, you can see those roots, that that go in to, you know, that branch out into the water. But when the area is is either flooded, or, or the you know, the vegetation has grown, you can't see those individual streams, the whole area just looks green and lush.

Christine Malec: 12:49

I want to try my hand at a bit of describing because this wasn't clear to me until I was able to check out a tactile map. And if I'm right, the Nile makes kind of a Y shape. So it's coming from south to north. And then when it hits the Mediterranean, it deposits all of this silt and soil and stuff to make this triangular formation of land so that you end up I think, at the Mediterranean, the Nile kind of splits around this triangular delta. So there's water flowing, sort of northeast and northwest around the delta. And so the delta is a triangular result of deposits from the Nile, is that right?

JJ Hunt: 13:31

Yeah, that's absolutely right. With the line coming up from the bottom, from from the South to the North, it's a little bit bendy, but it's, you know, more or less straight, and then you've got, you know, the v shape on top of that, that triangular shape on top of that, that triangle with the line coming at the bottom that's very much a Y shape.

Christine Malec: 13:49

And from a human perspective, what happens on Delta's like, Are there cities on that delta people live there? And if they do, is it a kind of a canal based area where you would need boats or a lot of bridges to get across the rivulets?

JJ Hunt: 14:05

Yeah, definitely, you need a lot of you need infrastructure to deal with this, right. So either because you are expecting flooding regularly, or because there just might be a flood at some point. Or because this is just wet land, you need to have, you know, ways to deal with that in some places where the canals in the Delta are clearer than you have. Yeah, then you have canal based systems where where people are traveling by boat, from place to place that just makes sense for their way of, of getting around in other places where you might just be needing, you might just be prepared for floods, as opposed to living without water day in and day out. And maybe you're going to you're going to build your infrastructure in a different way. I've got an image here, which is a flood plain. So it's not a Delta but it's a floodplain of the Nile. This is in Sioux, then and this image is it's quite something, it's a hazy picture. So it's a little bit hard to make out. The city that's in the background. So starts in the background, this hazy city, and jutting out toward us from the city is this point of green land with a few high rises on it. And then all around that point, really occupying the most of the image is flooded land. And it's, it's very difficult to say how large an area the flood is because the camera angle was clearly chosen to emphasize just how vast it is. And you know, so the camera angles playing a little bit of a trick on us. But it's a huge expanse of flooded land, this kind of muddy water, and then rising out of the muddy water, these little kind of organized pads of green, so they're kind of making little islands. And I don't know what this land would look like without the flood. But with it, it's just this big, huge muddy water like a big expanse. And then leading from the, that green point in the center coming, you know, that's coming toward us off to our right are two very long, thin bridges that from this angle look like they're barely above the water. So this is clearly how they've built their infrastructure. They know it's a floodplain, they know it's going to be flooding, you got bridges to get on and off this, you know, this green point in the middle, because it's likely that this floodplain has some water in it all the time. And right now, it's just at a high point where the water is right up to the green point. And you know, taking over the entire image.

Christine Malec: 16:48

As a historical geek moment, I want to point out that if you've read about the history of Egypt, you might know about lower Egypt and Upper Egypt. And it's counterintuitive, because Upper Egypt refers to closer to the head of the Nile, which is south and Lower Egypt is north, which refers to the lower, lower aspect of the river. And the the origin of the Nile is not actually an Egypt, right? It's, it's more in the southern part of Africa or the middle part of Africa.

JJ Hunt: 17:19

Yeah, yeah. Closer to the middle. So the Nile runs, like you say, north in East Africa. So it runs north, and it's in East Africa, it runs from Lake Victoria, which is in Uganda, and Tanzania. And it runs through South Sudan and Sudan, up through Egypt. And that's when it drains out into the Mediterranean. So I find it really helpful to have a mental picture of maps and landforms in my head, when I'm talking about different parts of the world. So let's try and make the continent of Africa a little bit easier to picture. Okay, so take your right hand and make a thumbs down. So your palm is facing away from you and the back of your hand that is pointed towards you. Now, open up your knuckles just a little bit so that you're not making a tight fist. So your knuckles are just kind of loosened, they're opened up a little bit. So your knuckles above the rings, if you've ring any rings, those are pointing to your left, your thumb is pointing down. That is kind of the shape of Africa. So your knuckles, those are Western Africa, your thumb, that's Southern Africa horn, yes, that's right. And that the top the pinky side of your hand, that's Northern Africa. Now, this isn't perfect, the thumb Southern Africa that is quite a bit bigger than your actual thumb like relative to the rest of your hand, that's a bigger chunk. But that's more or less where it's placed. And it does kind of it does stick down like that. That's the basic shape to the left of your thumb. That's the South Atlantic to the right of your thumb, that's the Indian Ocean, and your wrist, that's the Red Sea. The risk is the Red Sea, which separates Africa from Saudi Arabia. So the Nile in you know, relative to this hand, the Nile runs north from a more or less than knuckle on your thumb, which is inland but not very far from the eastern coast, it runs from your knuckle, all the way up across the back of your hand kind of more or less parallel to your wrist, which is more or less parallel to the Red Sea. And then it dumps into the Mediterranean Sea on the pinky side of your hand, just to the left of your wrist. And that journey from about your knuckle across the back of your hand. That's about 6800 kilometers 4200 miles.

Christine Malec: 19:46

Wow. And as a side note, when we did the episode on the Suez Canal, that's kind of roughly where the Suez Canal was going to the east of the Nile, right?

JJ Hunt: 19:55

That's exactly right. Because it's connecting that Red Sea there's a little tiny bit of Land paths the Red Sea that they had to break through it to get into into the Mediterranean. That's absolutely right.

Christine Malec: 20:09

So the Nile being a more or less straightforward image on a on a satellite map sort of heading from south to north. Let's talk about something that's maybe more complex. And the the Amazon I think is the is the largest river in the world by volume.

JJ Hunt: 20:26

Yeah, it is massive. So the Amazon cuts across the top of South America, the headwaters start on the mountains, which run down the west coast of the subcontinent. And then the main stem crosses Brazil and then empties into the North Atlantic on the East Coast. And, yeah, it is. It's enormous. It's about the network, the system covers about 7 million square kilometers, which for comparison, that's 10 times the size of France. It's enormous. It stretches from Colombia in the north Ecuador and Peru to the west and Bolivia and Central Brazil in the south, more water is discharged from the Amazon, then then the next seven largest rivers combined. Well, it's huge. So in satellite images, I needed to zoom out to about 5000 kilometers above the surface of the Earth, according to Google, to get the entire subcontinent wide base and on my laptop screen. And at that height, not many of the tributaries are clear. It's a big, fairly round patch that looks lush and really dark green, perhaps the darkest, most thoroughly green patch on all of Google Earth. But from this height, only the main stems are evident. In fact, they look like very fine brown lines that are overlaid on the image, like they look like border lines. It's only when you zoom in, and you see how squiggly those lines are that you realize, oh, wait a minute, those are waterways, those are borderlines, those are waterways, you need a diagram of the Amazon to really get a sense of how many tributaries, how many streams, how all of those are feeding into this main trunk, this main stem that cuts more or less horizontally across the top of the subcontinent?

Christine Malec: 22:29

No rivers do things to the land and land does things to the rivers? And is the Amazon a good example, to talk about those kinds of interactions over, you know, lots of time?

JJ Hunt: 22:41

I mean, there's so many different pathways that are coming together. And if you've got different kinds of different kinds of land different kinds of material like rock or how soft the rock is, or what's the vegetation that's already there, what's the climate, like, what's the elevation drop, all of those things will change how a river interacts with the land, and how the land forms the river and all of that. So for the Amazon, so I've got an image here of a sunset over what looks like a really wide Lake, there's just a hint of a tree line and the distance that are left and a hint of a tree line at a distance on a right. But at the center in the distance, it's open, there is no tree line. And that's the only hint that this is a river, not a giant lake, the water is not entirely hemmed in. Otherwise, this is a big, wide, calm looking Lake. You know, Lake body, and in fact, rivers do at some points, form lakes, and then just keep going. And that's that's what the Amazon looks like. In this particular image. In another photo, there are two very wide rivers that enter the image at our upper left, and they're just separated by this point of land, we just get a little tiny point of land up in the upper left. It's blanketed in like densely packed, lush green trees. And so there's a river on either side of this point of water that come together and they converge. And they form a single river that moves through the image down toward our lower right. So this is two rivers coming together to form an even larger river that's coming down. This larger tributary is also lined with thick, green rainforest. The scale of this image is it's massive, like it just looks like this, you know, thick blanket of green trees. And only when you zoom in, can you actually see one or two trunks and you realize, wow, if that's a trunk of the tree that large, there's nothing human built in here. So there's no way to to get the scale. It's only when you you see the the trunk of one of these trees when you zoom in that you realize that this is a massive scale. So then you can move to something like the Colorado so the Colorado is in a completely different climate. I'm starting it is starting in mountains the same way that that the Amazon is starting in mountains. But then it doesn't go through rain forest, the Colorado goes through desert, it goes through very different kinds of rock material. So the river looks quite different. So the Colorado starts in the central Rocky Mountains in the state of Colorado, and then flows southwest through you know, Canyon, specifically the Grand Canyon. The river doesn't quite make it out of the Colorado Delta anymore, it would have emptied into the Gulf of California. But at this point, it's tapped dry with dams and irrigation and basic urban water supply. So the Colorado delta is more or less dry at this point. And of course, one of the things that's so very impressive about the Colorado River is that it helped carve the Grand Canyon, so high in the mountains. That's where the headwaters are, it's lush and green up there. I've got an image here of a winding river, the shores dotted with evergreen trees, there are snow capped mountains in the distance very, you know, lovely, you know, typical mountain scene, it starts to gain strength, the Colorado River starts to gain gain strength from all of the tributaries, all of these mountains with their, you know, their snow capped mountains, all of that, that that snow was melting, rushing down, the river starts to get pretty swift. And that's when you get the classic whitewater streams or rivers right, churning water, rocky shores. And then as the Colorado moves south, the climate gets drier, and the river starts to encounter increasingly deep gorges of bare rock. And this is when we start getting the canyon landscapes that the area is very well known for red rock cliffs and gorges that are lined with the striations of the ages, very little vegetation, really just rock wall valleys and this river winding along at the bottom.

Christine Malec: 27:06

There's some terms in river talk that I don't understand. Can we talk about an Oxbow?

JJ Hunt: 27:13

Okay, so an Oxbow river can become an oxbow lake. So you know, the rivers we'll find, we'll find their path, right? When they're when they're rushing hard and they're high, their elevation drop is significant, they're going more or less straight, when they're slowing down. That's when you often get this winding this meander this back and forth, it's a very sin us kind of snake like back and forth, back and forth. And one of the things that that can do as it goes back and forth, the back and forth can get kind of loopy. So on each time that you're going, if you're basically making a figure eight shape with your finger, like you point your finger, just draw figure eight, it's kind of that kind of back and forth. But you're then moving forward, you're still you're still progressing. But those loops each time you make a loop and then turn around and loop in the other direction, you create a U shape. That is that's part of that meander. And if one of those, the back and forth, U shape connects, it can it can, you know, basically form a freestanding body of water in one of those loops that can then flood. So instead of just having this river outline, it joins as it as it kind of swoops back in. And that area will either create an island in the middle of a Round Lake, or the entire area can flood. And then it's and then you've just got a round pool that's at the side of another wise, you know, continuing to flow River.

Unknown: 28:53

What does it mean to say a rapids?

JJ Hunt: 28:57

So when you're up, usually higher in the river network. So when your your elevation drop is significant, the water is churning. That's that's a rapid, the water is rapidly moving through an area and they tend to have lots of rocks. So first of all, you've got to have a channel that can hold that kind of water movement, it won't turn into that kind of rapid. If you have a sandy bottom, for example, because it'll just wash all the way you generally need some kind of harder material on the sides of the bottom. Also, if you've got rocks, bigger rocks on the on the sides and bottom, the water is going to churn in a certain way. It's not just going to flow straight, like it's flowing down a pipe, there's more agitation, there's more movement in the water. And so then you get the water going rapidly down down slope, you've got the water hitting these rocks and churning, and that's when you get like white caps and you get little whirlpools and things so if you're white Got a rafting or something, you're looking for these kinds of areas that are navigable. But you know a little bit dicey because the water is going fast, it is churning, and there are rocks in the way. So that's what, that's what a rapids looks like.

Christine Malec: 30:20

On Saturday, August the 27th 2022, we'll be posting our last episode of Talk description to me. For now, the show was more popular than it's ever been. And we're still firmly committed to description rich programming. But there's been a tectonic shift in the financial position of the podcast, so we're going on hiatus to regroup and reimagine our model. The world of description is evolving fast, and funding models for creators and innovators haven't kept up. We're currently exploring new partnerships and envisioning new platforms that will not only allow us to keep creating content, but will also provide opportunities for other innovative creators, describers and allies to expand our collective view of what can be described and how we hope you'll stay subscribe to our podcast feed and our social media will be quieter, but we'll still be around. New episodes might pop up now and again, as world events unfold, and you can stay in touch with our other description related projects. We'll be closing our Patreon page for the time being limitless gratitude to those who stepped up to help support us, either with funds or with feedback. Stay tuned, there's more to come